Blast-furnace practice.



H. B. WEAVER & J. GAYLEY.

BLAST FURNACE PRACTICE.

APPLICATION FILED Aue.a. 1918.

1,292,937. Patented Jan. 28, 1919.

2 SHEETS-SHEET 1.

H. B. WEAVER 6r]. GAYLEY.

Patented Jan. 28, 1919.

2 SHEETS-SHEET 2.

5] nvemtozs: 42mm,

Has

UNITED STATES PATENT OFFICE.

HARRY B. WEAVER, 0F CATASAUQUA, PENNSYLVANIA. AND JAMES GAYLEY, OF

NEW YORK, N. Y,

BLAST-FUBNACE PRACTICE.

Specification of Letters Patent.

Patented Jan. 28, 1919.

To all whom it may con ern:

Be it known that we, Haney B. \VEAVER, a citizen of the United States.residing at atasauqua, Lehigh county, State of Pennsylvania. and JAMESGAYLRY, a citizen of the United States. residing at Yo. 555 Park arenue.in the city. county. and State of New York. have invented certain newand useful Imprm'ements in Blast-Furnace Practice; and we do herebydeclare the following to he a full. clear and exact description of theinvention such as will enable others skilled in the art to which itappertaius to make and use the same.

The eonstit uents of the customary charges regularly fed into an ironblast furnace consist of iron ore, limestone and coke, and containvarying percentages of alkali eom pounds, i. (a, compounds of otassiumand sodium. Descending in the furnace from a colder to a hottertemperature these alkali emupounds encounter the highest tempera ture inthe zone of combustion in the neighborhood of the twyers where theheated air blast comes in contact with the incandescent and an importantchemical reaction results.

The carbon of the coke and the nitrogen of the air blast cannot combineat the existing teunu-rature without the aid of an intermediar Thealkali-metals found in the furnace provide the most effective medium forbringing the nitrogen and carbon into combination in the combustion zoneand are present in said zone. The fact that potassium cyanid is formedin the blast furnace has been known. in fact, for a long time,

but has been regarded merely as an interesting chemical phenomenon, and,in so far as we are aware, it has not been known that it exists in theblast furnace in sufficient quantity to make it available for any usefulpurpose. nor that there were any other like compounds present whosewithdrawal would be feasible without detriment to the blast furnaceoperation. where certain essential conditions must be maintained inorder to permit the furnace to discharge its required functions in theproduction of its prescribed metallurgical product, that is to say. (ina pig iron blast furnace) its output of pig iron.

The present invention is based upon the discovery that, in addition topotassium cyanid, there are present in the furnace gases, at and in theneighborhood of the twyers, other compounds in which the alkali metalsare associated. and that the potassium cjyanid and these other compoundsare present in such quantity in the furnace and in such as' sociatioawith the reducing gases constantly rising from the zone of intensecombustion at or near the twyers that it feasible and remunerative towithd raw from the furnace a portion of the said reducing gases and toabstract therefrom by condensation or otherwise the compounds of thealkali metals so as to recover them in la rgre quantity for usefulpurposes, and without diverting from the blast furnace any suchtllnOLTl'll/Of the reducing gases as are required for serving theirpreparator function for the charge in the upper part of the furnaceshaft. Ac cordingly. the invention provides an opcration wherein theblast furnace delivers its normal output of pig iron and a normal slag,preserves the necessary conditions for the required reactions in thecombustion zone, permits the reducing gases rising from the combustionzone to exercise the required reducing action in the furnace shaft, and,coincident with these several necessary provisions for the successfuloperation of the iron blast furnace, permits the withdrawal andrecovery, on a commercial scale, of highly raluable compounds of thealkali metals, some of which were not known to exist in the con)-bustion zone of the blast furnace and which, in their entirety, were notknown to be present in sutlieient quantity to justify an attempt toremove them. or that paying quantities of any of such compounds wererecoverable while still preserving standard blast furnace conditions.

The recovery of these valuable constituents. in an efi'ective way, andwithout detriment to the normal functioning of the blast furnace isdependent upon factors of the furnace operation which we have taken intocareful account in working out the practice constituting thesubject-matter of the present invention.

Thus, the compounds of the alkali metals with carbon and nitrogen areformed, as hereinbefore indicated, in the zone of combustion in theneighborhood of the twyers,

where the heated air blast comes in contact with the incandescent fuel.On their formation, they pass upward in the furnace with the largevolume of reducing gases, thus meeting the colder charges of materialsproduced and before any important precipitation or disintegration takesplace in their upward travel. This zone of production is located in theneighborhood ofand in close proximity to the twyers, and, if thevaporized compounds are not withdrawn at or near their place offormation, they are lost. The urpose of the present invention is toprevent such loss, and to recover the products for useful purposes.

Accordingly, in carrying out the inven- V tion, a portion of thereducing gases containing a corresponding quantity of the vaporizedcompounds is withdrawn from the furnace at a point in the neighborhoodof the twyers, and preferably above them,

care being taken to restrict't quantity of the gases Withdrawn to anamount which will not interfere with the requirements of the reducinggases in the upper zone or shaft of the blast furnace. The furnaceoperator is enabled to judge of the limitations in this regard, bynoting, from time to time, the character and particularly the color of.the slag, which he may tap off, for that pur so, as a overnin test, atintervals, at tilib cinder gotch of the blast furnace. This slag (in apig-iron blast furnace) should normally be grav or white in color, thusindicating that only minute antities of iron appear in the slag, andthat the blast furnace is actin 7 under proper conditions which requiret at practically all of the iron in the carefully calculated ingre--dients of the charge shall be recovered in the metal output of thefurnace as pi iron. If the operator finds that the slag su stantiallyretains its normal gray or white color and substantially its normaltemperature and fluidity, he will know that the amount of the reducinggases withdrawn is within the limits that can be tolerated foracceptable blast furnace conditions, and also that the formation of therecoverable alkali metal com ounds is progressing normally in the comustion zone. If, on the other hand, he finds that the slag, in the testtap,

has assumed oris beginning to assume an abnormal darker tint, indicativeof the as-- Sage of oxid of iron into the slag, he wi be advised thatthe necessary conditions for the proper functioning of the blast furnaceare being interfered with by an excessive withdrawal of the reducinggases, and also that the formation, composition, and output of thedesired condensable products are suffering abnormal irregularities,correspondingly lnterferin with the intent and purposes of theinvention. He will, accordingly, be able to correct the irregularitiesreferred to, by appropriately limiting stricting the amount of thereduclng gas withdrawn, per unit of time, or by temporarily restoring,either wholly or partially, the usual blast furnace conditions, untilthe taking of a test at the cinder notch shows that the slag'has beenbrought back to normal. v

In some instances, the operator may prefer to withdraw continuously thepoltion of the reducing gases which it is found feasible to abstract forthe recovery of the compounds of alkali metals recoverable withoutinterfering with the necessary conditions of the blast furnaceoperation. In other cases, the operator may effect the withdrawal ofsuch quantities of the reducing gases, atintervals. Either of thesemodes of operation are within the broad purview of t e intendedpractice. Continuous or practically continuous withdrawal of the gaseswill be more advisable, in those instances where the quantity of alkaliin the charge is relatively large. Intermittent withdrawal is to be.recommended where the quantity of alkali in the charge is relativelysmall,the large capacity of the blast furnaces, with the high heatsemployed and the perfect reduction of the ores, causing even theordinarily small content of alkali in the charge to accumulate-inconsiderable quantity, and it may thus build up gradually in succeedingtime periods. so to make it feasible and even desirable to remove itapart. oreover, by the intermittent instead of the continuous withdrawalof the gas, furnace gas for the stack will be correspondingly conserved,thereby affording a Wider safety factor for the blast furnace operationas a whole. It will also be under stoodthat the recovery of thepotassium cyanid and other alkali metal compounds contained inthewithdrawn gases may be effected in any of the methods known to the art;that is to say, either by condensation. settling, screening, solution.electric precipitation. or the like. as will readily occur to thoseskilled in the art.

The withdrawal of the gases containing the products to be recovered inaccordance with our invention may. be through apertured plates or blocksinserted in the furor re-' eriodically at suitable intervals ion nacewall and )rovided with a water-corded passageway. '0 each of thesepiatcs or blocks conneetcd a conduit pipc leading to the condensing orrecovering apparatus.

In order to avoid comlensutitm of the oondensubie material in tlicconduit pipe it may have a heat insulating acket cithcr on thc. insideor on the ij'llbfiilli but if the insulation is on inside it .mue he ofa a torial resistant to the amino, of the g. and the vaporized compoundscarried thereby.

The condensing may be conducted in one or more chambers and in one ormore units as may be desired. Where the withdrawal of the gases is totake place continuously, it is. necessary to have more than one set ofchambers or units, so that when one set is being cleaned, another set,is available for operation. After the gases pass through the condensingapparatus, they are preierabl}. led through a flue of suitable length topermit them to cool down to a relatively lQ'iV temperature whereupon tlcy are led through a filter, such as a bag filter. or other analogousapparatus, for the further removal of the fume which carries values. Inpassing through the condensing apparatus, the gases will be reduccd 1ntempera ture, but if not sufficiently rcduccd in temperature to be iedimmediately to the filter, their passage through the due chow referredto. or through any like device. may be resorted to. as will be rcadiiyundi Md.

The final exit from the Eflt'ffl'fi paratus, practically freed of itssolid material, is not returned to the shaft of the fun nace, inasmuchthe intmrbictinn oi reintively ooldgas into the hot gases within thefurnace would accompiish no useful pun pose, and would even bedelctcrious for [lie reason that it would absorb heat. Act-or ingly, thefinal exit gas may citlier be wasted 01- may be led by a conduit to thestoves or boilers of the plant for heating purposes, as the necessitiesof the plant may require, or it can be put to other appropriate uses.

The air supplied to a blast furnace usually enters the tivyers at apressure of from 10 to 20 pounds per square inch. Accordingly. thepressure existing within the fur nacc will, in most instances. suiiiccFor insuring thc outflow of tlic portion of the gases to be withdrawntherefrom. and this outflow may conveniently be controiled by anadjustable valve or damper at the outlet of the condensing apparatus,the ratc of outflow of the withdrawn gases being so adjusted that thecomposition of the usual exit. gases from the furnace top is not apprwciably changed.

Referring further to the uses and practice of the invention, we maytnlrc. as an oxen:- ple. thereof, on n verage type of pigdron blastfurnace producing 400 tons of pig: iron daily. In such blast furnacethere will be consumed daily approximately 1300 tons of coke, ore andlinn stone, so that :1 relatively small content of alkali in thisaggregate will amount. in a days operation. to a considerable quantity.and may be withdrawn by the practne of tin present invention. at a ruleappr prints in tin: :illzai contents of the meta; .ai charged.

In a given instance. the charge ol a blast furnace showed on analysis anaverage of potash (calculated as K 0) 0.28%, and an average of soda{calculated as No. 0) 0.357.. These contents of potash and soda amountedper ton of iron produced to pounds of potash and 35 pounds of soda.Qucli a fun naoe charge can be enriched in potash, if desired. by thaddition of a pot'nsli-cm1taining mineml. such as green sand tusuall}containing about 8' of potash). providcd the t'urnace operations arenot. disturlocd from their proper function of producing pig iron.including the proper reduction of the iron ore, as indicated by the grayor white color of the slag. As hcrcinbctore noted, small amount of ironoxid in the slag suflices to turn it black. thereby indieatingabnormally iow tempcraturc conditions in the furnace. Moreover. such aslug necessarily an oxidizing and its pres rncc in the furnace tends toprevent the formation of cyanogen compounds which arc among the mostpowerful reducing agents known, so that the production of :1 black oroxidizing slag of itself indicates condi- News in the furnace that arciinfavorab'lc do the production of some of the compounds which it is thepurpose of the invention to recover,

The accompanying drawings illustrate col" tuin forms of appuratusadapted for currya suitable condensing system for the rceov cry of thealitalionctal and nitrogen compounds;

Fig. 2 represents :1 similar VitW showing a modified communication ofpiping ho tivccn the blast furnace and the first chamber of thecondensing! system:

Fig. 3 represents a sectional plan view of Fig. 2.

Rcfcrring to the drawings. 3 rcprcscnts a pigriron blast furnace.,uliicli. as ordinarilv constructed. is from 80 to 100 ft. high. 4rcprcscnts the twvcrs for the admission of the int air blast 5 thc slap:outlet or notch. and 6 thriron notch. 7 rcprcscnts cooled pintcs orblocks inserted in the hearth and bush wail of the furnace. throughwhich the poition of the reducing gases which. it is permissible toremove without disturbing the :isscntial blast furnace conditionsare'lso withdrawn together with their content of the compounds of thealkali metals which are to be recovered.

The oints of withdrawal of the gases are not limlted to the particularlocation of any of-the plates or blocks shown, but may be at any pointin the wall inclosing the combustion zone. Thus, as indicated in Fig.3,,

they may be spaced at substantially equal distances apart around theperiphery of the furnace, andmay all lead to the same initial chamber ofthe condenser system; in such case, instead ct; connecting the-severalblocks to a common bustle-pipe, individual pipes 9 will connect themseverally, in straight-line direction, to the condenser chamber, so thatit will be corres ondinglyconvenient to remove any possi le obstructionsthat might condense or otherwise form therein, and so that anyindividual pipe may be readily removed when occasion may require andsubduit 9, leading to the first condensin chamher 10 of the condensingsystem. he several blocks may, as shown in said figure, be connected toa manifold 8, for convenience and compactness of apparatus, instead ofbeing connected directly to the conduit 9 without using the manifold.

The gases entering the condenser 10, at an opening 11, deposit theheavier and more readily condensablc products therein and pass outthrough an outlet 12. In the construction of chamber 10, awater-container 13, which may be k t supplied from any convenient sourceof water (as. for instance, the valved pipe 13) is so arranged that theWater supplied thereto will flow over the upper edge of the containerand down over the periphery of chamber 10, thereby cooling the gaseswithin the chamber correspondingly and accelerating the condensationthereof. The waste water is collected in a gutter 14 at the low part ofthe chamber 10 and flows oil to waste at the discharge lip 15. 16 is anair valve which permits the air in the chamber 10 to escape when thegases are admitted to the chamber. 17 are lugs for lifting 'the chamberfrom its position. when desired, and substituting a fresh chamher. and,for this purpose, the joints 18 and 19 in the piping should preferablybe 'ball joints. Valves 20 and 21 are used for regulating the flow ofthe gas.

The gas asses from chamber 10 throu n conduit 22 into chamber 23, whichmay a so be water-cooled and wherein a further condensation of thecondensable compounds takes place, and at a lower temperature than inchamber 10. The material condensed in chamber 23 may be removed at thehopper bottom which has an aperture provided with a suitable valve, as,for instance, the conical' pivoted and counter-weighted valve 24.

T e velocity of the gases in the chamber 23 is comparatively low so thata considerable quantit of the condensable compounds is recovere in saidchanrber. From the chamber 23, the gases next pass through the conduit25, their flow being controlled by the adjustable valve 26. The conduit25 conducts the gases to a'bag filter or similar effective device inchamber 27-. The ba filter 28 will remove practically all of theremaining compounds which are carried along in suspension by the gases.The bag filter is provided with a ring 32 connected thereto, andoperating handles 29 extend through the walls of the chamber so that theworkmen mayshake the bag filter by means of these handles,-therebydislodging the material within the .bag which material thereupon fallsinto the receptacle 30. The gases, after havingpassed through thefilter, make their exit at 31 and can lie-carried oil to any convenientplace of use.

It will be noted that the exit pipes from thechambers 10 and 23 extenddown to the lower portion of said chambers, so as to give the gases alonger path to travel before taking their exit therefrom. In passingfrom the chamber 23 to the chamber 27, the gas must be so far lowered intemperature that it will not consume or injuriously affect the materialof the filter bag. This can be done by cooling the conduit 25 in anyappropriate manner, as, for instance, by Water jets evternally appliedthereto, or, (in substitution or connection therewith) by extending thelength of the conduit so that the gases will have a sufiicient length oftravel to efi'ect the necessary reduction in tern erature.

The condensing system i lustrated is typical of many others that mightbe substituted therefor. The quickly condensable com ounds, which areheavier, are deposited in c amber 10. Those that are lighter and requirefurther cooling, are deposited in chamber 23. and the compounds insuspen sion are recovered in chamber 27. The condensation and collectionof the compounds may therefore be said to be fractional. and thetemperature of the gases is lowered successively from one chamber toanother to permit this fractional recovery of the compounds. 7

A typical instance will illustrate the prac tical results obtained bythe practice of the invention. Thus, operations were conducted on apig-iron blast furnace 80 ft. high and 17 ft. 6. in. in diameter at thebosh and with a hearth 11 ft. 6 in. The data for a weeks operation ofthis furnace were as follows:

Volume of air blast per minute:23,000 cu. ft. Temperature of air blastl200-1300 degrees Fahr.

30 per cent. of the ore charge was Lake Superior ores. and per cent. NewJersey magnetites. The vaporized compounds of the alkali metals werewithdrawn from a point above the twyers and led to a. condensingapparatus. and from there to a bag filter.

The material. collected in that part of the apparatus preceding thefilter was found. on analysis, to give the following percentages ofpotassium cyanid and other alkali metal compounds, to wit:

Potassium cyanid (KCN) :24.35)?

Carbonate of potash (K CO 31.272

The material obtained from the filter portion of the apparatus gave thefollowing pen centages of potassium cyanid and other alkali-metalcompounds. to wit:

Potassium cyanid (KCN) :49.05; Carbonate of potash (KfiOQ QlB-fifi. Soda(Na O):6.20EZ.

These analyses illustrate the commercial and industrial capabilities ofthe invention. They also illustrate, in a striking manner, the facthereinbefore indicated. that there are present in the hearth and bosh ofthe iron'blast furnace not only alkali cyanid but other compounds inwhich the alkali metals are associated and that these are there presentin large quantity and in recoverable form as potassium. carbonate, andalso as sodium compounds (calculated as (Na O). In so far as we areaware, even the presence of these additional compounds, as such, in thecombustion zone of the iron blast furnace, has never before beenestablished, nor their recovery effected.

It will, of course, be understood that by the expression iron blastfurnaces as used in the claims. we do not intend to exclude iron blastfurnaces whoseproduct may vary from pi iron. inasmuch as the blastfurnace charge is frequently made up in such manner as to result in aproduct containing notable quantities of alloying metals. such asmanganese, silicon. or the like.

In further explanation of the characteristic feature of thepresentinvention, we may point out that, in blast furnace practice, itis absolutely necessary to maintain the thermal equilibrium or heatbalance, which is relatively sensitive, in order to obtain the standardmetal product of the blast furnace operation. The thermal equilibriumcan, perhaps, best be understood from the point of view that the blastfurnace consists of two separate pieces of apparatus, the onesuperimposed upon the other; the upper apparatus, is that in which,occur the preheating and reduction of the iron ore and other ingredients of the charge. while the lower apparatus is the hearth andbosh. in which the melting of the iron and cinder and the removal of thefinal traces of oxygen, etc, are carried on. these being operationswhich can only occur at a certain (high) critical temperature.

The gas resulting from the combustion of the fuel in the lower apparatusmust supply the heat necessary for both sets of reactions. or thefurnace will not function according to its prescribed intent.

It so happens that the ordinary heat requirements of these two pieces ofapparatus are proportioned to one another in approximately the samerelations as the heat available from the gases of combustion. Thesegases yield a. small quantity of high temperature heat in cooling fromtheir theoretical combustion temperature to the critical temperature.and a much larger quantity of heat in cooling from the criticaltemperature to the temperature at which they are discharged. There isgenerally an excess for the latter purpose: in fact. the conditions ofsafest furnace operation demand that there shall be such an excess.'This is for the following reason:

The amount. of heat used in the shaft of the furnace is, roughly, fiveor six times the amount used in the hearth. Broadly speaking. about5,000 thermal units per pound of iron are used in the shaft and about1.000 thermal units per pound of iron in the hearth. A deficiency of agiven number of thermal units would, therefore. be about five times asgreat. measured as a. percentage, in the hearth as in the shaft. Thus,if the descending charge were short in its heat requirement by 500thermal units to the pound of iron at the base of the shaft, this wouldonly be a deficiency of about 10% but when the charge entered the hearththis would eonstitute about a. 50']? deficiency of the. heat requirementin \that region. This would be absolutely ruindus to the work of thefurnace and would put it out of working commission completely. From thisreasoning it can be seen that it is vital that the charge shall enterthe hearth without any de ficiency in the heat which it should receivein the shaft and this limits radically the amount of gas which can beabstracted from the base of the shaft. Generally}.

where coke is used as the fuel in the charge, the surplus of thermalunits in the shaft is considerable,roughly speakin from 10 per cent. upto 20 per cent, un er ordinary conditions. This surplus can beabstracted from the shaft without detriment to the working of thefurnace. For instance, it is well known that a certain amount of watercan be added to the charge without affecting the work of the furnace,but if this amount be exceeded, the effect becomes highly injurious.

It will therefore be understood that in order to abstract the potassiumcyanid, the potassium carbonate, and the sodium compounds, andnevertheless maintain the normal operation of the furnace for itsprimary purpose, which is emential for commercial operations. the amountof heat abstracted must be within the margin of surplus availablewithinthe shaft.v

It is therefore possible to operate the furnace in either of the twoways hereinbefore described, for the recovery of the potassium cyanid,potassium carbonate and sodium compounds, without upsetting the thermalequilibrium. Thus, an amount of gas within the safe margin indicated maybe continuously abstracted from the bosh; or, intermittently, relativelylarge portions of the gas may be abstracted for limited periods, theperiods of withdrawal being separated by suitable time intervals, sothat the drain upon the furnace shall not exceed the margm of safety.Any greater abstraction than this by either method would result inupsetting the thermal equilibrium of the furnace and would cause theconditions in the hearth to pass from completely reducing to partlyoxidizing, owing to the resence of a considerable quantity of hig lyoxidizing iron oxid, which passes into the slag when the conditions inthe hearth are not sufliciently reduging. This would not only upset thework of the furnace and spoil the iron roduced, but would probablymaterially re uce the amount of cyanid produced, since the oxidizingaction of the slag in such case would tend to destroy it.

We may say further. that we regard the intermittent withdrawal of thegases for the recovery of the alkali compounds as presenting particularadvantages, even in those instances where it would be feasible towithdraw the gases continuously. For instance, the removal of the gasescontinuously involves the removal of a correspondingly small percentageof gases, per unit of time; so that there is a tendency to clog up thesmall aperture or apertures through which the gases are withdrawn, and,at the same time, the relatively slight draft on the zone ofconcentration of the alkali compounds, tends to limit the withdrawal ofthe compounds to a more or less local region in the vicinity of theaperture or apertures. On the other hand, the intermittent operation, bypermitting the accumulation of the alkali compounds up to acertain pointof saturation, enables the operator to remove a larger proportion of thegas, with a high percentage of the alkali compounds, during a relativelyshort interval, and the attendant high velocity of the withdrawn gasesnot only tends to prevent clogging of the apertures through which theypass, but also insures a deeper draft on the zone of concentration ofthe alkali compounds; so that, by the intermittent process, practised atsuch intervals as will not disturb the thermal conditions of the blastfurnace, a high recovery of the alkali com ounds is assured, even thoughthe analysis of the furnace char e is relatively low in alkali.

What we claim is:

1. The method of operating iron blast furnaces, which consists incarrying on the blast furnace process to produce iron and slag as usual,and to produce by a heated air blast supplied under pressure anatmosphere of reducing gas in contact with the ignited fuel, withdrawingfrom the furnace such portions of the reducing gases as are notnecessary for maintaining the required reducing conditions in the stack.and abstracting from said withdrawn gases the compounds of the alkalimetals contained therein.

i 2. The method of operating iron blast furnaces, which consists incarrying on the blast furnace process to produce iron and sing as usual,and to produce by a heated air blast supplied under pressure anatmospllcrc of reducing gas in contact with the ignited fuel,withdrawing from the furnace such portions of the reducing gases as arenot necessary for maintaining the required reducing conditions in thestack, an abstracting from said withdrawn gases he compounds of thealkali metals contained therein, the withdrawal of the reducing gasesbeing effected at a point in their u ward travel below that at which thesaid compounds would be precipitated or disassociated by the coldermaterials in the furnace.

3. The method of operating iron blast furnaces, which consists incarrying on the blast furnace process to produce iron and slag as usual,and to produce by a heated air blast supplied under pressure anatmosphere of reducing gas in contact with the ignited fuel, withdrawinfrom the furnace such portions of the re ucing gases as are notnecessary for maintaining the required reducing conditions in the stack,and abstracting from said withdrawn gases the compounds of the alkalimetals contained therein, the withdrawal of the reducing gases takingplace periodically so as to perfurnaces, which air blast,

mit the building up or accumulating of said compounds therein in theperiods of time between withdrawals.

4. The method of operating iron blast furnaces, which consists incarrying on the blast furnace process to produce iron and slag as usual,and to produce by a heated air blast supplied under pressure, anatmosphere o reducin gas in contact with the ignited fuel, regu atingthe operation so as to maintain sla of a light color, withdrawing fromthe reducing gases as are not necessary for maintaining the requiredreducing conditions in the stack, and abstracting from said withdrawngases the compounds of the alkali metals contained therein.

5. The Method of operating iron blast consists in carrying on the blastfurnace process to produce iron and slag as usual, and to produce by aheated supplied under pressure, an atmosphere of reducing gas in contactwith the ignited fuel, withdrawing from the furnace a portion of thereducing gases containing alkali carbonate at a rate which will notdestroy the thermal equilibrium of the furnace, and abstracting fromsaid withdrawn gases the alkali carbonate contained therein.

6. The method of operating iron blast furnaces, which consists incarrying on the blast furnace process to produce iron and slag as usual,and to produce by a heated air blast supplied under pressure, anatmosphere o reducing gas in contact with the ignited fuel, withdrawingfrom the furnace urnace such portions of thea (portion of reducing gasescontaining a. so ium compound at a rate which will not destroy thethermal equilibrium of the furnace, and abstracting from said withdrawngases the sodium compound contained therein.

7. The method of operating iron blast furnaces, which consists incarrying on the blast furnace process to produce iron and slag as usualand to produce by a heated air blast supplied under pressure anatmosphere of reducing gas in contact with the Ignited fuel, permittingthe building up or accumulation of alkali compounds within said gases,and periodically withdrawing the major part of the alkali compounds thusaccumulated together with such limited amount of reducing gases as willnot destroy thethermal equilibrium of the furnace, and abstracting thealkali compounds from the withdrawn gases.

In testimony whereof I, HARRY B. WEAV- ER, aliix August, 1918.

HARRY B. WEAVER.

Witnesses:

E. C. Koons, A. E. BROWN. In testimony whereof I, JAMES GAYLEY, afiix mysignature on this second day of August, 1918. i

' JAMES GAYLEY. Witnesses:

WALTER S. Rune, F. W. Your.

my signature on this sixth day of

